Machines that produce very long electrical discharges find use in a wide variety of applications including industrial equipment testing, basic research and scientific demonstrations. Typically these Extra-High Voltage (EHV) machines comprise large transformers, capacitor banks or electrostatic induction machines such as Van De Graaf generators.
For lightning susceptibility tests of equipment, the device under test is typically placed within striking range of the EHV generator and electrically grounded. Long electrical discharges from the EHV generator ultimately find their way towards and attach to the device under test. The current that passes through the body of the device and the concentrated heat at the attachment point of the arc are configured to simulate of the effects of a natural lightning strike. These tests are often performed on critical items such as aircraft, fuel tanks, antenna structures, and emergency shelters.
For scientific research applications, long arc discharges are used in experiments to perform atmospheric electricity studies, weather modeling, and characterization of geospace components such as the ionosphere and the Earth Schumann Resonance. Long arc discharges also find use in many scientific demonstrations for the general public, providing viewers a rare glimpse of the spectacular dynamics and destructive potential of long electric arcs in air, and their effects on familiar items such as electronics, vehicles, and buildings.
Long electrical arcs in the range of three to three hundred meters in length are required for most demonstrations and testing applications. Under normal conditions, electrical arcs greater than 3 meters in length require drive voltages of at least 350,000 volts. For larger scale applications, operating voltages can extend into the megavolt range. The embodiments of the invention disclosed herein provide methods for generating localized electrical discharges greater than 3 meters in length, fulfilling the needs of most testing, research and demonstration applications.
EHV machines typically comprise large, permanent facilities, since they must necessarily support heavy high-voltage components and maintain large clearance distances. A standard six megavolt impulse generator for testing power grid equipment can reach over 20 meters in height and weigh many tons. As a consequence, existing EHV facilities are limited to applications where the equipment to be tested can be transported to the EHV discharge generator itself.
Clearly, a collapsible large-scale electrical discharge generator capable of economic transport and deployment could fulfill many new and useful services, including testing of items that are difficult to move such as large aircraft, or permanent items such as buildings and equipment installations. The embodiments of the invention disclosed herein provide a number of novel innovations towards realizing a practical, collapsible and transportable large-scale EHV electrical discharge generator.
An induction coil provides one method for generating high voltage electrical discharges. A rapidly changing magnetic field passing through the induction coil generates a corresponding voltage between the ends of the coil. For large induction coil dimensions and fast moving magnetic fields, millions of volts can be realized. Variants of this method include adding resonant circuitry to the induction coil, which can modify the effective output impedance and improve overall efficiency in certain applications.